Kinetics of chlorite dismutase in a perchlorate degrading reactor sludge

Perchlorate bioreduction in UASB reactor: S2--autotrophic granular sludge formation and sulphate generation control

Perchlorate (ClO4-) industrial wastewater requires efficient removal to prevent adverse environmental impacts, however, high concentration and low biodegradability give rise to poor ClO4- bioreduction performance. S2--autotrophic granular sludge (S2--AuGS) was firstly cultivated for high concentration perchlorate (ClO4-) removal in the upflow anaerobic sludge blanket (UASB) reactor (ClO4-: 150 mg L^-1). Simultaneously, the S2- was utilized to control the SO42- generation as electron donor, the effluent SO42- concentration (190 mg L^-1) was satisfied with drinking water standard (250 mg L^-1). Under the optimized condition of hydraulic retention time (HRT) (6 h) and S2-/ClO4- molar ratio (2.2), more EPS was secreted, which promoted the S2--AuGS formation and stability. Though acclimation of 146 d, the S2--AuGS was formed with a large average granular sludge size (612 μm) and an excellent settleability (sludge volume index: SVI₅/SVI₃₀= 1). With the mature S2--AuGS formation, the highest ClO4- and S2- loading was increased to 1.06 and 0.75 kg m^-3 d^-1. Interestingly, Georgfuchsia, Methyloversatilis, Sulfurisoma, and Exiguobacterium were the main microbial community in the S2--AuGS. This study proposed to form a novel S2--AuGS for developing the high ClO4- concentration removal performance and to utilize the S2- as an electron donor for controlling the excessive SO42- generation.

Perchlorate as an emerging contaminant in soil, water and food

Perchlorate ( [Formula: see text] ) is a strong oxidizer and has gained significant attention due to its reactivity, occurrence, and persistence in surface water, groundwater, soil and food. Stable isotope techniques (i.e., ((18)O/(16)O and (17)O/(16)O) and (37)Cl/(35)Cl) facilitate the differentiation of naturally occurring perchlorate from anthropogenic perchlorate. At high enough concentrations, perchlorate can inhibit proper function of the thyroid gland. Dietary reference dose (RfD) for perchlorate exposure from both food and water is set at 0.7 μg kg(-1) body weight/day which translates to a drinking water level of 24.5 μg L(-1). Chromatographic techniques (i.e., ion chromatography and liquid chromatography mass spectrometry) can be successfully used to detect trace level of perchlorate in environmental samples. Perchlorate can be effectively removed by wide variety of remediation techniques such as bio-reduction, chemical reduction, adsorption, membrane filtration, ion exchange and electro-reduction. Bio-reduction is appropriate for large scale treatment plants whereas ion exchange is suitable for removing trace level of perchlorate in aqueous medium. The environmental occurrence of perchlorate, toxicity, analytical techniques, removal technologies are presented.